EP3637070A1 - Dispositif et procédé de détermination de la géométrie d'observation - Google Patents

Dispositif et procédé de détermination de la géométrie d'observation Download PDF

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Publication number
EP3637070A1
EP3637070A1 EP19194783.7A EP19194783A EP3637070A1 EP 3637070 A1 EP3637070 A1 EP 3637070A1 EP 19194783 A EP19194783 A EP 19194783A EP 3637070 A1 EP3637070 A1 EP 3637070A1
Authority
EP
European Patent Office
Prior art keywords
capturing device
image
optical capturing
viewer
light source
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP19194783.7A
Other languages
German (de)
English (en)
Inventor
Larry E. Steenhoek
JR Robert V. CANNING
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Axalta Coating Systems GmbH
Original Assignee
Coatings Foreign IP Co LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Coatings Foreign IP Co LLC filed Critical Coatings Foreign IP Co LLC
Publication of EP3637070A1 publication Critical patent/EP3637070A1/fr
Pending legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/255—Details, e.g. use of specially adapted sources, lighting or optical systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J3/50—Measurement of colour; Colour measuring devices, e.g. colorimeters using electric radiation detectors
    • G01J3/504—Goniometric colour measurements, for example measurements of metallic or flake based paints
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0278—Control or determination of height or angle information for sensors or receivers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J3/463—Colour matching
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/0304—Detection arrangements using opto-electronic means
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/70—Determining position or orientation of objects or cameras
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/90—Determination of colour characteristics
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/60—Control of cameras or camera modules
    • H04N23/698—Control of cameras or camera modules for achieving an enlarged field of view, e.g. panoramic image capture
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/46—Measurement of colour; Colour measuring devices, e.g. colorimeters
    • G01J2003/466—Coded colour; Recognition of predetermined colour; Determining proximity to predetermined colour
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10024—Color image
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • H04N23/741—Circuitry for compensating brightness variation in the scene by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors

Definitions

  • the description generally relates to visual color harmony evaluation of repaired articles or OEM vehicles at the end of the assembly line. Particularly, the description is directed to systems and methods for determining illumination angle and viewing angle in color observation.
  • the surface coatings can utilize one or more pigments or effect pigments to impart the desired color or appearance, such as solid, metallic, pearlescent effect, gloss, or distinctness of image, to the vehicle bodies.
  • Metallic flakes, such as aluminum flakes are commonly used to produce coatings having flake appearances such as texture, sparkle, glint and glitter as well as the enhancement of depth perception in the coatings imparted by the flakes.
  • the system for determining illumination angle and viewing angle in color observation includes, but is not limited to, an optical capturing device configured to acquire an image of its surroundings; a processing unit connected to the optical capturing device by a data transmission link and configured to: identify a position of a light source in the image acquired by the optical capturing device; identify a position of a viewer in the image acquired by the optical capturing device; determine a first angular position of the light source with respect to the optical capturing device and a second angular position of the viewer with respect to the optical capturing device and provide the first angular position and the second angular position to define an actual viewing geometry.
  • the method for determining illumination angle and viewing angle in color observation includes, but is not limited to, positioning an optical capturing device at an area to be audited; acquiring an image by the optical capturing device of its surroundings; identifying a position of a light source in the image acquired by the optical capturing device; identifying a position of a viewer in the image acquired by the optical capturing device; determining a first angular position of the light source with respect to the optical capturing device and a second angular position of the viewer with respect to the optical capturing device and providing the first angular position and the second angular position to define an actual viewing geometry.
  • Coupled means that one element/node/feature is directly or indirectly joined to (or directly or indirectly communicates with) another element/node/feature, and not necessarily mechanically.
  • drawings may depict one exemplary arrangement of elements, additional intervening elements, devices, features, or components may be present in an embodiment of the depicted subject matter.
  • certain terminology may also be used in the following description for the purpose of reference only, and thus are not intended to be limiting.
  • processor devices can carry out the described operations, tasks, and functions by manipulating electrical signals representing data bits at memory locations in the system memory, as well as other processing of signals.
  • the memory locations where data bits are maintained are physical locations that have particular electrical, magnetic, optical, or organic properties corresponding to the data bits.
  • FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • FIG. 1 A block diagram illustrating an exemplary computing environment in accordance with the present disclosure.
  • module or “unit”, especially the processing unit, refers to any hardware, software, firmware, electronic control component, processing logic, and/or processor device, individually or in any combination, including without limitation: application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
  • ASIC application specific integrated circuit
  • processor shared, dedicated, or group
  • memory executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.
  • pigment refers to a colorant or colorants that produce color or colors.
  • a pigment can be from natural or synthetic sources and can be made of organic or inorganic constituents. Pigments can also include metallic particles or flakes with specific or mixed shapes and dimensions. A pigment is usually not soluble in a coating composition.
  • effect pigment refers to pigments that produce special effects in a coating.
  • effect pigments include, but not limited to, light scattering pigments, light interference pigments, and light reflecting pigments.
  • appearance can include: (1) the aspect of visual experience by which a coating is viewed or recognized; and (2) perception in which the spectral and geometric aspects of a coating is integrated with its illuminating and viewing environment.
  • appearance includes texture, coarseness, sparkle, or other visual effects of a coating, especially when viewed from varying viewing angles and/or with varying illumination conditions.
  • Appearance characteristics or appearance data can include, but not limited to, descriptions or measurement data on texture, metallic effect, pearlescent effect, gloss, distinctness of image, flake appearances and sizes such as texture, coarseness, sparkle, glint and glitter as well as the enhancement of depth perception in the coatings imparted by the flakes, especially produced by metallic flakes, such as aluminum flakes.
  • Appearance characteristics can be obtained by visual inspection or by using an appearance measurement device.
  • Color data can further comprise a color code of a vehicle, a color name or description, or a combination thereof.
  • Color data can even further comprise visual aspects of color of the coating, chroma, hue, lightness or darkness.
  • the color data can be obtained by visual inspection, or by using a color measurement device such as a colorimeter, a spectrophotometer, or a goniospectrophotometer.
  • spectrophotometers obtain color data by determining the wavelength of light reflected by a coating layer.
  • the color data can also comprise descriptive data, such as a name of a color, a color code of a vehicle; a binary, textural or encrypted data file containing descriptive data for one or more colors; a measurement data file, such as those generated by a color measuring device; or an export/import data file generated by a computing device or a color measuring device.
  • Color data can also be generated by an appearance measuring device or a color-appearance dual measuring device.
  • coating can include any coating compositions known to those skilled in the art and can include a two-pack coating composition, also known as "2K coating composition”; a one-pack or 1K coating composition; a coating composition having a crosslinkable component and a crosslinking component; a radiation curable coating composition, such as a UV curable coating composition or an E-beam curable coating composition; a mono-cure coating composition; a dual-cure coating composition; a lacquer coating composition; a waterborne coating composition or aqueous coating composition; a solvent borne coating composition; or any other coating compositions known to those skilled in the art.
  • the coating composition can be formulated as a primer, a basecoat, or a color coat composition by incorporating desired pigments or effect pigments.
  • the coating composition can also be formulated as a clearcoat composition.
  • vehicle can include an automobile, such as car, bus, truck, semi-truck, pickup truck, SUV (Sports Utility Vehicle); tractor; motorcycle; trailer; ATV (all-terrain vehicle); heavy duty mover, such as, bulldozer, mobile crane and earth mover; airplanes; boats; ships; and other modes of transport.
  • SUV Sports Utility Vehicle
  • heavy duty mover such as, bulldozer, mobile crane and earth mover
  • a matching formula refers to a collection of information or instruction, based upon that, the coating composition can be prepared.
  • a matching formula includes a list of names and quantities of pigments, effect pigments, and other components of a coating composition.
  • a matching formula includes instructions on how to mix multiple components of a coating composition.
  • gonioapparent paint materials relates to such paint materials that are known to exhibit changes in color and appearance with changes in illumination and viewing geometries. This phenomenon is the root of the term gonioapparent and is defined in ASTM E284, Standard Terminology of Appearance as pertaining to change in appearance with change in illumination or viewing angle. In order to characterize the color and spatial appearance of gonioapparent materials it is necessary to measure their color at a variety of different measurement geometries.
  • this invention can also be used for visual color harmony evaluation of other articles, especially of articles with gonioapparent paint materials of which the appearance depends on the illumination angle and viewing angle.
  • Some examples of such coated articles include, but not limited to: home appliances, such as refrigerator, washing machine, dishwasher, microwave ovens, cooking and baking ovens; electronic appliances, such as television sets, computers, electronic game sets, audio and video equipment; recreational equipment, such as bicycles, ski equipment, all-terrain vehicles; and home or office furniture, such as tables, file cabinets.
  • articles without coating that have color and appearance include, but not limited to, engineering polymers, injection molding plastics or polymers, or other synthetic materials.
  • FIG. 1 shows a system 10 for determining illumination angle and viewing angle in color observation.
  • the system 10 comprises an optical capturing device 20 configured to acquire an image of its surroundings.
  • the system 10 comprises a processing unit 30 connected to the optical capturing device 20 by a data transmission link 25.
  • the processing unit 30 comprises a processor 36, a display 32, and an input device 34.
  • the display 32 is configured to display optical information to an operator.
  • the input device 34 is configured to receive input data from the operator.
  • the processor 36 is configured to identify a position of a light source in the image acquired by the optical capturing device 20, identify a position of a viewer in the image acquired by the optical capturing device, determine a first angular position of the light source with respect to the optical capturing device and a second angular position of the viewer with respect to the optical capturing device and provide the first angular position and the second angular position to define an actual viewing geometry.
  • the input device 34 can be selected from a digital input device, such as a wired keyboard, a wireless keyboard, a digital writing pad, a touch screen, an input portal that can be connected to an electrical device or another computer, or any other digital devices that can input data into the computing device; an optical input device, such as a barcode reader, a scanner, a digital camera, a digital video camera, or any other optical devices that can input data into the computing device; an electromagnetic input device, such as a radio receiver, an RFID (radio frequency identification) receiver, an infrared data receiver, or any other devices that can receive data through a broad range of electromagnetic wavelengths; or a combination thereof.
  • a digital input device such as a wired keyboard, a wireless keyboard, a digital writing pad, a touch screen, an input portal that can be connected to an electrical device or another computer, or any other digital devices that can input data into the computing device
  • an optical input device such as a barcode reader, a scanner, a digital camera, a digital video camera, or any other
  • Each of the data input devices may further require necessary adaptors or couplings in order to input data into the processor 36 or processing unit 30, wherein those adaptors or couplings can be readily determined by those skilled in the art. Those adaptors or couplings can further be wired or wireless.
  • the display 32 can be selected from a digital display device, such as a computer monitor, a PDA, a computer, a cell phone, a smart phone, a tablet computer, or a TV; an optical display device, such as a projector; a print display, such as a printer; or a combination thereof.
  • the display device can also be a dual functional display/data input device.
  • One example of such dual functional device is a touch screen of a computer, a smart phone, a tablet computer, or a PDA.
  • the optical capturing device 20 can be a camera, preferably for taking still images.
  • the camera may operate in the visual range of light but may also work in the infrared range at a wavelength between 1 mm and 780 nm.
  • the camera comprises camera optics and components to take an image.
  • the camera is a digital camera.
  • the camera may comprise an optical sensor like a CCD-sensor (charge coupled device).
  • the camera comprises a memory unit to store the acquired images.
  • the camera transmits the image data to the processing unit 30 via the data transmission link 25.
  • the data transmission link 25 may be wired or wireless and may be designed as a unidirectional or bidirectional link.
  • the processing unit 30 may transmit commands to the camera via the data transmission link 25.
  • the system 10 further comprises a remote control 22 that is communicatively connected to the camera via a control link 23.
  • the control link 23 may be a wired or wireless link.
  • the camera 20 may be triggered to acquire a picture.
  • the operator may change the viewing position and carry the remote control.
  • a still image may then be taken whenever it is desired by pushing a button of the remote control 22.
  • This provides a lot of flexibility for using the system 10 described herein. For example, when a color mismatch is detected, the operator may take a picture from that point where the mismatch is seen.
  • the system determines the viewing geometry (illumination angle, viewing angle) so that the conditions when the mismatch is detectable are determined.
  • the system 10 for determining illumination angle and viewing angle in color observation comprises an optical capturing device 20 configured to acquire an image of its surroundings; a processing unit 30 connected to the optical capturing device 20 by a data transmission link 25, wherein the processing unit 30 is configured to identify a position of a light source in the image acquired by the optical capturing device; identify a position of a viewer in the image acquired by the optical capturing device; determine a first angular position of the light source with respect to the optical capturing device and a second angular position of the viewer with respect to the optical capturing device and provide the first angular position and the second angular position to define an actual viewing geometry.
  • the viewer may be a person or an automated detecting unit that is positioned at a certain position with respect to the article and detects the optical appearance of the article.
  • the detecting unit may capture an image of the article and may transmit it to a second display unit so that an operator is allowed to verify the optical impression of the article from the position of the detecting unit.
  • an image is acquired from the perspective of an audited area of an article so that any light source or light sources as well as a viewer can be identified to determine the position of the light source (or light sources) and the viewer in order to determine the specific lighting and viewing conditions.
  • the angular positions of the light source and the viewer are determined based on the acquired image.
  • the system may take an image in case the viewer finds that there is a mismatch between the color of the audited area and the surroundings of the audited area. In that case, the viewer may trigger the optical capturing device to take a picture.
  • the optical capturing device 20 may be removably attached to the area to be audited, e.g., surface of a vehicle.
  • the optical capturing device 20 may comprise one or more manually removable vacuum cups or magnets to attach the device 20 to the surface to be audited or close to the surface to be audited.
  • the optical capturing device may be attached to the surface to be audited such that a normal to the surface to be audited is parallel or coincides with a normal to the optics of the optical capturing device.
  • a relative angle of the light source with respect to the surface to be audited corresponds to the relative angle of the light source with respect to the optics (in particular the lens) of the optical capturing device.
  • the viewing geometry is defined by the relative position of the light source and viewer with respect to the area to be audited, i.e., with respect to the optical capturing device.
  • the optical capturing device 20 is a camera configured to acquire an image with a field of view of 180° or less.
  • the camera may have a field of view of 165° which may be sufficient to acquire the positions of the light source and the viewer under the typical viewing conditions.
  • the camera may be equipped with a so-called fisheye-lens in its optics.
  • the optical capturing device 20 is configured to acquire a high dynamic range (HDR) image.
  • HDR high dynamic range
  • Bright light sources may saturate the signal of standard dynamic range images. This saturation area can be quite large, making it difficult to pinpoint the center of the light source in the image. HDR images on the other hand are much less prone to image saturation than are standard dynamic range images and therefore it is easier to properly select the center of the light source.
  • the processing unit 30 is configured to determine a first polar angle of the light source in the acquired image.
  • a polar angle defines the position of an object on a sphere that is defined by the field of view of the optical capturing device. The polar angle is further described with reference to Figs. 4 to 6 .
  • the polar angle of the light source particularly defines the viewing geometry because it describes the relative position of the light source and the optical capturing device which is attached to the area to be audited.
  • the processing unit is configured to determine a first azimuth angle of the light source in the acquired image.
  • the azimuth angle is used to further define the relative position of the light source with respect to the optical capturing device.
  • the processing unit is configured to determine a second polar angle of the viewer in the acquired image.
  • the processing unit is configured to determine a second azimuth angle of the viewer in the acquired image.
  • the second polar angle and the second azimuth angle define the position of the viewer in the acquired image.
  • system further comprises a remote control configured to trigger acquiring the image by the optical capturing device.
  • the viewer can take an image when he or she is at a specific position.
  • the viewer may change their position and audit the vehicle while the viewer can take an image (one or more images) by using the remote control whenever desired.
  • the remote control is portable so that the viewer can carry it when changing a viewing position.
  • the remote control is connected to the optical capturing device by a control link.
  • system further comprises a display configured to display the acquired images and/or the first angular position and/or the second angular position.
  • the processing unit is a computer or laptop or a portable device like a smartphone or a tablet having a monitor/display so that the acquired image can be displayed.
  • system further comprises an input device configured to indicate the position of the light source and/or the position of the viewer.
  • an operator may manually indicate the position of the light source and/or viewer.
  • a pointer may be moved within the image by a mouse or by a keyboard to the light source and to the eyes of a viewer to indicate the specific positions of the light source and the viewer in the image.
  • the positions of the light source and the viewer correspond to the position of the pointer as positioned by the operator within the image.
  • the position may be indicated by touching a specific position in the image on a touchscreen.
  • Fig. 2 exemplarily shows a typical measurement geometry.
  • the area to be audited is generally shown at 101 and may be a coated surface or part of a surface of a vehicle. Rays of light are reflected by the surface 101 and may influence the optical appearance of the surface 101.
  • Light source 103 for example the sun or an artificial light source with a defined spectrum of light, emit light rays towards the surface 101.
  • the specular reflection of the light rays is shown at 105 with the angle of incidence 104 of the light rays of light source corresponding to the angle of reflection 106 of the specular reflection.
  • Three detectors 107, 109, 111 are arranged at defined positions: the first detector 107 is arranged at 15° from specular reflection, the second detector 109 is arranged at 45° from specular reflection, and the third detector 111 is arranged at 110° from specular reflection.
  • the angular position of the detectors is provided in a direction from the specular reflection towards the light source.
  • the detectors 107, 109, 111 may be an appearance measurement device as described above.
  • Fig. 3 shows an exemplary situation where a surface 101 to be audited is observed by a viewer 113 under specific lighting conditions defined by the position of the sun 103. If, under this condition, the viewer 113 observes a mismatch of repaired sections of the surface of the car and the surroundings of these repaired sections, it does not necessarily mean that the mismatch can also be observed under different lighting and viewing conditions. It is necessary to determine the specific viewing geometry (position of the light source and the viewer with respect to the audited surface) in order to determine the cause of the mismatch.
  • Fig. 4 shows in-plane and out-of-plane geometries.
  • "O” defines the point of origin of the coordinate system and particularly corresponds to the position of the optical capturing device.
  • the optical capturing device captures a hemispherical image with a given field of view.
  • the field of view is 180° as shown by the circle (base area) defined by the points "A", “D", “C", and “E”. However, the field of view may be smaller than 180°.
  • the illumination ray "IO” and the sample normal "BO” define the specular plane "ABC”. Viewing ray "OR1" lies in the specular plane.
  • the specular reflection "OS” also lies in the specular plane.
  • "S"', “R1'", and “I'” are the projections of "S", “R1", and “I”, respectively, onto the base area.
  • Viewing ray "OR2" lies out of the specular plane in the plane "DBE".
  • the polar angle of "R1" corresponds to the angle between the base area and "OR1".
  • the polar angle can be determined by determining the position of the projection "R1" in the base area.
  • the polar angle can be determined in the image taken by the optical capturing device.
  • the azimuth angle of "R2" is the angle between "AC” and "DE”.
  • Fig. 5 schematically shows an image taken by the optical capturing device.
  • the light source 103 is positioned on the right of the horizontal axis and the viewing point is on the left.
  • the polar angle of the light source is at about 45°, see polar angle lines 115 from 10 to 70°, where 80° corresponds to the outermost circle and 90° corresponds to the circumferential border of the schematic image.
  • the azimuth angle is shown at 117.
  • the azimuth angle of the light source is 0° and the azimuth angle of the viewer is 180°.
  • the polar angle of the viewer is 30°.
  • Fig. 5 basically corresponds to the "BOR1"-scenario shown in Fig. 4 .
  • Fig. 6 shows an alternative image that corresponds to the "IOR2"-scenario of Fig. 4 .
  • the viewer is out of the specular plane.
  • the position of the light source 103 did not change while the position of the viewer 113 changed.
  • the polar angle of the viewer is still 30° but its azimuth angle is now about 210°.
  • the system 10 can be calibrated by mapping spherical coordinates of imaged hemisphere onto 2D-images.
  • the optical capturing device is attached (preferably removably attached) to the object to be audited with surface normal of optical capturing device coincident with surface normal of the object.
  • An image (preferably fisheye image) of the environment is acquired from the perspective of the object surface at or close to a point of audit.
  • the light source and viewer are identified in the 2D-image and the locations of light source and viewer are mapped to spherical coordinates. This allows calculating a position direction of specular reflection and also calculating an effective aspecular angle and flake angle of viewing geometry. This process may be repeated for each light source, if multiple light sources are involved. Intensity weighting may be required to estimate effective geometry.
  • the system may comprise a computer program product that is executed by the processing unit, especially by a processor of the processing unit, so that said steps are carried out.
  • Fig. 7 shows how the effective flake polar angle of a given geometry is derived and especially shows the specular plane for the case of illumination ray AB and viewing ray B'C. Allowing for refraction of the light as it enters and exits the paint film, only flakes that are oriented with flake normal polar angle of HKJ will act as specular reflectors. It is the proportion of flakes that lie at each polar angle that determines the flop characteristic of the specimen.
  • the effective flake normal polar angle for a particular illumination and viewing geometry may best describe the geometry and not the aspecular angle.
  • Fig. 8 shows 2D mapping and calibration of the image taken by the optical capturing device.
  • a 2D-fisheye photo of a calibration hemisphere is shown with the polar angle calibration lines.
  • "B” corresponds to 10°, "C” to 20°, etc.
  • spline interpolation of polar angle ⁇ is shown. The distance in pixels from the center of the left drawing is determined and based on the number of pixels, the polar angle ⁇ is determined. The points B, C, D, ..., G are measured points and the dotted line is the spline interpolation.
  • the number of pixels may depend on the characteristics of the optical capturing device and that the number of pixels may vary. However, this does not alter the basic concept that a given number of pixels corresponds to a specific polar angle.
  • the azimuth angle can be determined in a similar manner than the polar angle.
  • the azimuth angle may be determined based on the number of pixels at a specific distance (e.g., the distance of the viewer) from the center point of the image. Particularly, the number of pixels of a full circle at the distance of the viewer (radius of this full circle) is determined and corresponds to 360°. Then the number of pixels between the horizontal line and the viewer along the circle line is determined and based on the ratio (pixels of full circle) / (pixels of partial circle) the azimuth angle is determined.
  • the 2D-mapping and the spline interpolation may be executed by a computer program product that is executed by the processing unit.
  • the system 10 described herein relates to a device for field use to record and determine illumination angle and viewing angle in color observation.
  • the device can comprise an imaging system, such as a camera with a fisheye lens to record illumination lighting and observation positions.
  • the device can further comprise a computer program to map spherical coordinates of the illumination and observation positions to record illumination angle and viewing angle.
  • the computer program can further produce flake angles and effective/actual viewing geometry.
  • Fig. 9 schematically shows the steps of a method for determining illumination angle and viewing angle in color observation.
  • the method comprises the following steps: in a first step, shown at 210, positioning an optical capturing device at an area to be audited; in a second step, shown at 220, acquiring an image by the optical capturing device of its surroundings; in a third step, shown at 230, identifying a position of a light source in the image acquired by the optical capturing device; in a fourth step, shown at 240, identifying a position of a viewer in the image acquired by the optical capturing device; and in a fifth step, shown at 250, determining a first angular position of the light source with respect to the optical capturing device and a second angular position of the viewer with respect to the optical capturing device and providing the first angular position and the second angular position to define an actual viewing geometry.
  • Any function of the system 10, especially of the processing unit, may be implemented as a method step, and vice versa.

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EP19194783.7A 2018-09-18 2019-08-30 Dispositif et procédé de détermination de la géométrie d'observation Pending EP3637070A1 (fr)

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US9734635B1 (en) * 2015-07-13 2017-08-15 Amazon Technologies, Inc. Environment aware color visualization

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